Manufacture of lubricating oils



Patented 18, 194

I MANUFACTURE or LUBBICATING oms Arthur Lazar, Berkeley, and John 6. Carter; on;

cord, Calif., assignors to Tide Water Associated Oil Company, San Francisco, Calif., a corporation of Delaware Serial No. 492,134

No Drawing. Application June 24 1943,

1 This invention relates tocompounded lubricating oils containing omdati'on and corrosion inhibitors and more specifically to lubricating oils containing metal saltsiof petroleum sulphonic acids and primarily intended for use in the lubrication of internal combustion engines.

It is now common in themanufacture t lubricating oils intendedfor heavy duty service, such as, for example, the so-called high speed" Diesel engines, to employ addition agents ion the purpose of improving the oil in one or more of the following characteristics: I I (1) Resistance to oxidation and sludge formation.

(2) Cleanliness of engine, and resistance to piston ring sticking.

lei-claims.- .(01. 252-33).

I 2 strong sulphuric acid whereby the most readily sulphonated constituents are converted into sulphonic acids, part of which remain in the oil.

- .These oil-soluble acids are then removed from the oil by treatment with aqueous sodium hydroxide or other alkali whereby they are converted into water-soluble alkali metal sulphonic salts which dissolve in the aqueous caustic soda and leave a refined hydrocarbon oil. The process to the sulphonic salts being entirely secondary. According to general practice, the alkali metai sulphonic salts derivedas above are. converted into .(3) Oiliness, or resistance to scoring or scuiiing.

(4) Resistance to corrosion of the working parts of the engine, particularly to alloy bearings of the copper-lead type.

The above characteristics are desirable in lubrieating oils subjected to less severe service and,

' has resulted in the trial of various combinations of additives for securing the desired result. Polyvalent metal salts of sulphonic acids derived from petroleum, particularly those of the alkaline earth metals, have been found to be particularly usethe desired polyvalent metal sulphonate by treat ment with a water-soluble inorganic salt'of the required metal. The water-insoluble metal sulphonate precipitates from the aqueous solution as a voluminous mass which readily retain appreciable quantities of unreacted sodiumsulphonate and other impurities which are very clif-v flcultto remove, even by prolonged washing with boiling water. Sodium' sulphonate is thus retained as an impurity in the desired metal sulphonate and, when the latter is added to a lubrieating oil, has been found to be very detrimental the oil an appreciable afilnity for, moisture and in} in supplying the desired properties to lubri-.-

sult of higher speeds and higher compression pressures, as a result of which oils compounded with metal sulphonates, as customarily manur factored, have been unable to supply the desired characteristics to the desired degree. In accordance with the present invention, it has been found that. by "proper processing, oils containing metal sulphonates can "be prepared with greatly enhanced ability to provide for engine cleanliness and with markedly increased freedom from corrosion. s

In the conventional method of manufacturing,

metal sulphonates for use as additives in lubricatingl oils. a raw petroleum distillate is treated with results in an increased tendency toward rusting rity also may be avoided by manufacturing the desired metal sulphonate directly in the' oil as described by Bergstrom in U. S. Patent 2,270,577. In this procedure a suitable lubricating stock is treated'with concentrated or fuming sulphuric acid, thereby producing sulphonic acids dissolved in the oil. After separating the acid sludge, the sulphonic acids are neutralized directly in the oil with oxide or hydroxide of the required polyvalent metal. By following this procedure, the oil is both purified and provided with the additive simultaneously without the necessity of the intermediate production of alkali metal sulphonates.

In preparing oils of greatly enhanced antisludging, anti-ring-sticking, and anti-corrosion properties compounded with polyvalent metal salts of petroleum sulphonic acids in accordance with the present invention, it is important to avoid any contaminationwith alkali metal sulphonate as such contamination will counteract to a large extent the advantages gained by the invention. The invention, therefore. contemplates the use of some such method, or other method which may suggest itself, for preparin polyvalent metal sulphonate free from alkali metal contamination. method described by Bergstrom is preferred, in some respects, due to the simplicity of'manufacturing steps involved.

Hitherto, in the preparation of polyvalent metal sulphonates for use as addition agents in lubrieating oils, paramn base oils have been gre ly preferred as the source from which the sulphonic acids are to be derived, regardless of Whether the sulphonate is finally to be blended into paraifln base oil, into naphthene base oil, or into a blend of paraflin and naphthene base oils. This is principally because metal sulphonates made from sulphonic acids derived from the sulphonation of naphthene base oils usually exhibit a highly corrosive action toward alloy bearings, especially those of the copper-lead type, particularly after long periods of operation in the engine. Also, oils compounded with metal sulphonates derived from naphthene base oils frequently do not possess the resistance to oxidation commonly exhibited by similar oils compounded with metal sulphonates derived from parailin base oils. On the other hand, the yield of sulphonic acids from naphthene base oils is, in most cases, about double that obtainable from paraifin base oils except under the most excessive sulphonating conditions. Accordingly, if it were not for the above mentioned disadvantages of metal sulphonates derived from naphthene base oils, such oils would be far more economical as a source of the sulphonic acids, both because of the greater yields obtainable and-because of their relative cheapness.

The present invention provides a mean whereby naphthene base oils may be properly selected and treated to yield sulphonic acids and polyvalent metal sulphonates at least equal to those derived from paraflin base oils with respect both to resistance to oxidation and freedom from corrosion. As a consequence, greater yields of polyvalent metal sulphonates, for use as addition agents in lubricating oils, have been made possible from relatively inexpensive, and hitherto unsatisfactory, raw material. In a particular form of the invention excellent results are ob-: tained by deriving the sulphonic acids from properly selected and treated mixtures of parafiin and naphthene base oils, all of which is hereintaining from naphthene base oils polyvalent metal The above-mentioned 4 sulphonates superior to those customarily made therefrom.

Other objects will be ing description.

We have found that, to a great degree, corrosive action is imparted to lubricating oils containing metal sulphonates by the presence of minute quantities of other metal salts, especially those 'of naphthenic acids and of other acidic substances generally present in oils of naphthenic origin. On sulphonation of-naphthenic oils, these acidic substances are only partially removed by the sulphuric acid treatment, or they may even apparent in the followundergo sulphonation themselves. Consequently,

an appreciable quantity remains in the oil in their original form or as sulphonated acids and thus contaminate the sulphonic acids formed. Whether the sulphonic acids are converted to polyvalent metal'sulphonate directly in the oil or whether they are first extracted from the sulphonated oil and subsequently converted to polyvalent metal sulphonate, the acidic impurities or their reaction products will simultaneously be converted to their corresponding metal salt which will contaminate the metal sulphonate and make the same corrosive to alloy bearings. By carefully removing these acidic impurities from naphthene base oils prior to sulphonation it is found that such oils, upon subsequent sulphonation, yield oil soluble sulphonic acids which may be converted to polyvalent metal sulphonate having excellent freedom from corrosion.

Further, we have found that polyvalent metal sulphonates derived from the sulphonation of the lower boiling naphthenic base oils do not provide as great a degree of freedom from ringsticking and resistance to oxidation as provided by metal sulphonates derived from the sulphonation of parafiin' base oils or the higher boiling naphthenic base oils. On the other hand, alkaline earth metal sulphonates made from sulphonic acids derived from the sulphonation of high molecular weight oils exhibit an ability to maintain engine cleanliness to a greater degree than metal sulphonates derived from low molecular weight oils.

The advantages obtainable by utilizing the above discoveries are illustrated in the following table which shows the results of comparative runs made on a single cylinder Diesel engine and a four cylinder Diesel engine, both having copper-lead bearings, using an S. A. E. 30 blend of naphthene and paraflln base oil containing 3% of calcium sulphonate prepared in various manners.

Run A was for -a duration of 240 hours in the four cylinder engine using an oil compounded with calcium sulphonate derivedfrom the sulphonation'of a 1000 sec. S. U. F. naphthene base oil from which naphthenic acids were not removed.

Run B was for a duration of 240 hours in the four cylinder engine using an oil compounded with calcium sulphonate derived from the sulphonation of a 1000 sec. S. U. 100 F. naphthene base oil from which naphthenic acids had been previously removed.

Run 0 was for a duration of 240 hours in the four cylinder engine using an oil compounded with calcium sulphonate derived from the sulphonation of a 100 sec. 8. U. 100 F. naphthene base oil from which naphthenlc acids were not removed.

Run D was for a duration of hours in the single cylinder engineusing anoilsimilarto tha used in run A.

RunE was for a duration of 120 hours in the single cylinder engine using an oil similar to that used inrunB.

Run F was for a duration of 120 hours in the single cylinder engine using an oil similar tothat used in run C. Y

Table Appearance of engine Clean. Very clean.

Accordingly the invention, in its broader as-" pects and in brief, comprises the following steps: (a) Selection of a high boiling naphthene base oil for sulphonation;

Lacquer on iston skirts. Clean. p

- clean. n l; w: badlylgaquamd,

(b) Removal of naphthenic acids and other tabulation may be combinedinto a single stepby forming the po y alent metal sulphonate directly in the oil, providing, of course, that'tlze oil selected in step (a) is suitable for use in'the finished oil;

The naphthene base oil selected for'sulphonaof fuming sulphuric acid-per barrel will be required and for oils containing hisher percentages of sulphonic acidsflflgher rates of sulphuric acid per barrel are The temperature of the treatment may vary from below atmospheric up to about 200 F., a higher degree of suiphonation being obtained at the higher temperatures. Any method of agitation of the acid with the oil is suitable, although mechanical agitation; in a closed system is preferred, particularly'when elevated temperatures are employed. Agitation with air may be used, but is less desirable because of the tendency, more pronounced at elevated temperatures, to initiate oxidation reactions. The use of air may also involve the loss of appreciable quantities of B02. In order to obtaineiiicient mixing of high viscosity oils, the oil should be diluted with a low viscosity oil of great resistance to sulphonation. For this purpose a highlyacidtreated light oil, such as kerosene or transformer oil, may be used, it being the purpose to reduce the viscosity without introducing any material which will produce sulphonic acidsother than those desired. After treatment with the acid for a sufllcient length of time, the acid sludae is com-. pletely separated from the oil. In order to sep-.

arate the last traces of sludge, centrifuging or oil in suitable proporshould, as stated tion should have at least about 90%. of its constituents boiling above 3'15" F. at 2 lnmJlg absolute pressure; Under conventional methods of fractionally distilling lubricating oil stocks this would correspond to an'oil having a viscosity above about 400 seconds S. U. at 100 F. However, an oil having a principal boiling range above 435 F. at 2 mm. Hg absolute pressure is preferred. Such a preferred oil would have a viscosity of 900 to 3000 seconds 8. U. at, 100 F.

The oil so selected is first freed from naphthenic acids and other acidic bodiesgwhich may be accomplished by prolonged treatment withaqueous caustic alkali. Alternately, and preferably, the acidicbodies-may be removed by distillation, under reduced partial pressure, in the a portion. of the naphthenic acids, such treat- 7 ment, either before or after the above caustic treatment, is desirable to remove the more reactive constituents of the oil which might otherwise form unstable sulphonation products.

The 011 thus freed from the unstable impurities is treated with concentrated sulphuric acid, preferably between 98% H2804 and 15% free S03. The acid rate used for this treating step is from two pounds per barrel up to 100 pounds per barrel, depending upon the quantity of sulphonic acids desired in the treated oil. For an oil confiltration may be required.

Following sulphonation the sulphonic acids contained in the oil may be removed from the oil, converted to the required polyvalent metal sulphonate and the latter added to the desired lubricating oil in the required proportion; or the sulphonic acids may be converted to the required metal sulphonate directly in the oil.

If it is desired to separate the acids, the separation and conversion to the metal sulphonate results are generally obtained with from 1% to.

5%. Oils containing higher percentages of metal sulphonate may be manufactured and later blended with other suitable oil to meet the de- Such blending may be done by the manufacturer prior to sale or it may besired percentage.

5% of metal sulphonate are intended to come v within the scope of the invention.

In the event that itis desired to convert the sulphonic acids to the polyvalent metal sulphonate directly in the oil, the sulphonated 011 after complete-removal of the acid sludge is contacted with anoxiderhydroxide, or water-soluble inorganic salt of the particular metal desired to be incorporated into the oil as an oil-soluble sulphonate. The preferred metal for this purpose is one of the alkaline earths, especialLv calcium.

.tation iscontinued until the neutralization is complete,-which point may, if desired, be detertaining 1% of sulphonicacids, about 15 pounds I! mined readily by simple laboratory test. Followabqtve be performed so as to directly in the oil attention should be given to certain features which are unimportant when the metal sulphonate is prepared separately and added to the lubricating oil.

First, the oil selected for sulphonation must also be chosen with regard to its suitability as the major constituent of the finished lubricating oil. The characteristics of naphthene base oils are well known in the art and proper selection for any given purpose is within the skill of the by the well known Edeleanu process, or other solvent refining process, are preferred by the trade, and such oils are well adapted for the present purposes. The sulphonation step and the presence of the metal sulphonate change the viscosity butlittle and any such change not anticipated may be adjusted by a final blending or reduction if desired.

Second, the degree of sulphonation should be carefully controlled so as to produce the required amount of sulphonic acids to produce the concentration of metal sulphonate desired in the finished oil. The required degree of sulphonation may be readily determined by simple laboratory tests for any given oil. It has been found expedieat and, therefore, is a preferred embodiment of the invention, to deliberately carry the sulphonation beyond the desired concentration of sulphonic acids and, after conversion of the acids to metalsulphonate, to blend with the treated oil a sufiiciently quantity of any suitable oil to produce the required concentration of sulphonate in the final blend. By proper choice of blending oil the viscosity and viscosity-index of the final blend can be controlled simultaneously with the concentration of sulphonate. As an example, a naphthenic base oil having a viscosity approximating S. A. E. 50 and a viscosity-index of about 30 may be sulphonated to yield as high as 10% of sulphonic acids dissolved in the oil, exclusive of the diluent used to reduce the viscosity as described above. At this point further sulphonation becomes very difiicult. After conversion of the sulphonic acids to metal'sulphonate and removal of the diluent, the oil may be blended with an S. A. E. 10 oil having a viscosity index of 100 (parafiin base oil) to give a finished oil containing 4% to 5% of metal sulphonate with an 8. A. E. 30 viscosity and a viscosity-index of 70. The

' exact concentration of metal sulphonate in any such treated oil may be readily determined by an ash analysis.

In the foregoing description it has been shown that polyvalent metal sulphonates prepared from sulphonic acids derived from the sulphonation of specially selected and treated naphthene base oils have, when blended into lubricating oils, excellent ability to prevent oxidation and maintain engine cleanliness. It has also been pointed out that greater yields of sulphonic acids may be obtained from the sulphonation of naphthene base oils than from paramn base oils. In accordance with a particular embodiment of the invention, it is contemplated to sulphonate blends of parafiln base and naphthene base oils; providrefiner. Ordinarily, oils which have been refined ing, of course, that the naphthene base oil in the blend is of high boiling range and has been freed from acidic impurities in accordance with the principles described above. Due to the higher yields of sulphonic acids obtainable from the naphthene'base constituent of the blend, such a blend will yield the major portion of sulphonic acids from the naphthene base constituent even when the percentage of paraffin base oil in the blend is as high as 70%.

Hitherto it has not been deemed advisable to derive metal sulphonates from such blends due to the undesirable characteristics customarily exhibited by the metal sulphonates derived from the naphthene base constituents. By treating the naphthene base constituent of the blend in accordance with the principles outlined above, advantage can be taken of the greater yields ob- .tainable over those obtainable when sulphonating straight parafiln base oils. This may be utilized to advantage when it is desired to prepare polyvalent metal sulphonate directly in the oil and the finished oil is required to have a viscosity index substantially greater than that of naphthenic oils. In such a case one may advantageously select a highboiling naphthene base oil, free the same from naphthenic acids and other acidic impurities, blend therewith the required amount of parafiin base oil to obtain the desired viscosity-index, sulphonate the blend, and

.convert the sulphonic acids to polyvalent metal sulphonate, as described above for naphthene base oil alone. By selection of a high viscosity naphthene base oil and a low viscosity paraffin base oil for such purpose the use of the diluent may be, in general, dispensed-with as the viscosity of the blend will normallybe sumciently low to'permit efllcient mixing with the sulphonating agent. Following is an example of the preparation of a compounded lubricating oil in this manner:

220 gallons of a California lubricating distillate having a'viscosity of 3000 seconds 8. U. at 100 F. which had been Edeleanu treated were distilled under vacuum in the presence of 5 gal-' ions of 40- B..caustic sodasolution to remove naphthenic acids and to yield 215 gallons of purlfied oil. To the purified oil was added 285 gallons of Pennsylvania neutral having a viscosity of 200 seconds 8. U. at 100"v F. The resulting blend was agitated with 300 pounds of fuming sulphuric. acid containing 15% free for a period of one hour during which time the temperature rose from F. to F. The acid sludge was removed by settling following which the last traces of sludge were removed by centrifuging. The sulphonated oil was then agitated with 80 pounds of Ca(OH)z to which was added 10 gallons of water. The agitation was continued for three hours at a temperature of 80 F., following which the water was flashed off and excess lime was removed by filtration. This yielded a finished oil having the following properties:

Viscosity, sec. S. U. 100*! 537 Viscosity-index, Dean and Davis '19 Ash, percent as 09.804 0.35 Estimated calcium sulphonate, percent.... 3.5 Bearing corrosion after hours in single cylinder Diesel engine, mg '13 Appearance of engine Excellent In the foregoing description the formation of oil soluble sulphonic acids from-petroleum oils has bocndcscribedasbeingwccomplishcdbysulphonationwith concentrated sulphuric acid. By concentrated sulphuric acid, 66 B. acid up to fuming acid containing 50% free S03 is meant; although, as stated prior, a concentration between 98% H280! and 15% free S: is preferred. However, other sulphonating agents may be used. For example, chlorosuiphonic acid, or sulphuric acid in conjunction with certain water absorbing ingredients, such as phorsphorous pentoxide, may be used to aid the sulphonation process.

As stated prior, the scope of the invention includes oils cont'aininghigh percentages of sulphonate for use as stock solutions which are to be later blended with suitable oil to yield the required concentration of sulphonate. When it is desired to prepare such stock solutions and it is likewise desired to convert the sulphon-ic acids to the polyvalent metal sulphonate directly in the oil, the oil after neutralization with the metal oxide, hydroxide, or salt, may be subjected to a distillation with fire and steam, preferably under vacuum, .for the purpose of concentrating the additive by distilling ofi part of the oil. In this manner the soap content of the residual oil can easily be brought to the desired concentration within a wide range. It is found that, by such concentration processfthe stability of the s'ulphonate additive is further improved. Such concentration causes the breakdown of the less stableconstituents of the sulphonate with a resulting precipitation of a small quantityof inorganic matter, which should preferably be filtered from the oil. If desired, such concentration may be conducted in the same operation as the dehydration step.- Likewise, if a low boiling oil is used to reduce the viscosity during sulphonation as described previously, the subsequent removal of the same may be combined with the concentration, if desired.

The terms parafiin base oils and naphthene base oils are used herein in accordance with the customary practice of the petroleum industry to differentiate oils with respect to their dominant characteristics. Paraflin base is applied to oils typical of those derived from Pennsylvania crude oils. These are characterized by having a high viscosity index and relatively high boiling range for a given viscosity. On the other hand, naphthene base oils have low viscosity indices, relatively low boiling ranges for a given viscosity, and generally contain appreciable quantities of naphthenic acids, phenols, and the like; Typical examples of naphthene base oils, to which the invention is particularly adapted, are. those. derived,

from California crudeoils, especially those produced in the San Joaquin Valley.

Oils are known which have properties intermediate between the true naphthene and parafiln types. These are generally referred to as mixedbase oilsi For the purposes of this invention such "mixed-base oils are tobe considered the equivalent of naphthene base oils providing they contain appreciable quantity of naphthenic acids or similar organic acids. If naphthenic acids are absent, such oils may be used, if desired, instead of the parafiin base 'oils' in the herein.

Unless otherwise specified, the terms high boiling and high molecular weight applied herein to petroleum oils are intended to mean oils of blends described 10 As applied. to sulphonic acids, thereof, similar terms maybe used according to the molecular weight, or boiling range, of the petroleum oil from which the suiphonic acids ar derived.

In the claims the terms polyvalent metal base and alkaline earth metal base are used to denote an oxide, hydroxide, or salt of a polyvalent metal or alkaline earth metal respectively, suitable for converting sulphonic acids into the corresponding metal sulphonate.

1. A method of preparing a, lubricating oil having reduced tendency toward oxidation, ringsticking, and corrosion which comprises: 'removing napthenic acids and other acidic substances from a naphthene bas oil whose principal constituents haveboiling points above 375 F. at 2 mm. Hg absolute pressure, treating the purified oil with a sulphonating agent to provide sulphonic acids dissolved in the oil, removing the spent sulphonating agent, converting the sulphonic acids to polyvalent metal sulphonate free of alkali metal sulphonate and incorporating the same in a hydrocarbon lubricating oil in oxidation inhibiting amount.

' 2. A method according to claim 1 in which the I principal constituents of the naphthene base oil have boiling points above 435 F. at 2 mm. Hg

sufllciently high molecular weight that the main constituents thereof boil above about 375 F. at 2 mm. Hg absolute pressure. Similarly. low boiling and low molecular weight" oils mean oils boiling below :uch .empent :e at said presmre.

mm. Hg absolute pressure, treating the purified absolute pressure.

3. A methodaccording to claim 1 in which the sulphonating agent is concentrated sulphuric acid.

4. A method according to claim 1 in which the sulphonating agent is sulphuric acid having a concentration between 98% H2804 and 15% free- SOa. I

- 5. A method according to claim 1 in which the amount of polyvalent metal sulphonate in the finished oil is in excess of 1%.

6. A method according to claim 1 inwhich the polyvalent metal sulphonate isan alkaline earth I sulphonate.

7. A method according to claim 1 in which the polyvaient metal sulphonate is calcium sulphon ate.

base oil by distillationat reduced pressure in the presence of caustic soda.

9. A method of preparing a lubricating oil havoil with a, sulphonating agent to provide sulphonic acids dissolved in the oil, removing the spent sulphonating agent, removing the sulphonic acids from the oil and converting said acids to polyvalent metal sulphonate while avoiding the formation of any alkali metal sulphonate, andadding the po'lyvalent metal sulphonate to a hydrocarbon lubricating oil in oxidation inhibiting amount.

10. A method of preparing a lubricating oil hav-' ing reduced tendency toward oxidation, ringst icking, and corrosion which comprises: removing naphthenic acids and other acidic substances from a naphthene base oil whose principal constituents have boiling points above 375 F. at 2 oil with a sulphonating agent to provide sulphonic acids dissolved in the oil in amount greater than 0.1%, removing thelpent sulphonatlng agent,

or metal salts 8. A method according to claim 1 in which the f naphthenic acids are removed from the naphthene 7 11 treating the oil containing sulphonic acids with a polyvalent metal base to convert the sulphonic acids to polyvalent metal sulphonate dissolved in the oil, and removing any unreacted polyvalent metal base.

11. Ame'thod oi preparing a lubricating oil having reduced tendency toward oxidation, rin sticking, and corrosion which comprises: removing naphthenic acids and other acidic substances from naphthene base 011 whose principal constituents have boiling points above 375 F. at 2 mm. Hg absolute pressure, treating the purified oil with a sulphonating agent to provide sulphonic acids dissolved in the oil in amount greater than 0.1%, removing the spent sulphonating agent, treating the oil containing sulphonic acids with an excess of lime in th presence of water to convert the sulphonic acids to calcium sulphonate dissolved in the oil, and removing th water and the unreacted lime.

12. A method according to claim 11 in which the sulphonation produces sulphonic acids dissolved in the oil in amount greater than 1.0%.

13. A method of preparing a lubricating oil having reduced tendency toward oxidation, ringsticking, and corrosion which comprises: removing naphthenic acids and other acidic substances from a nahpthene base oil whose principal constituents have boiling points above 375 F. at 2 mm. Hg absolute pressure, blending the purified oil with a paraflln base oil in amount not greater than 70% of the blend, treating the blend with a sulphonating agent to provide sulphonic acids dissolved in the blend, removing the spent sulphonating agent, removing the sulphonic acids from the blend and converting said acids to polyvalent metal sulphonate while avoiding the formation of any alkali metal sulphonate, and adding said polyvalent metal sulphonate to a hydrocarbon lubricating oil in oxidation inhibiting amount.

'14. A method of preparing a lubricating oil having reduced tendency toward oxidation, ringsticking, and corrosion which comprises: removing naphthenic acids and other acidic substances from a naphthene base oil whose principal constituents have boiling points above 375 F. at 2 mm. Hg absolute pressure. blending the purified oil with a paramn base oil of lubricating oil viscosity in amount not greater than 70% or the blend, treating the blend with a sulphonatin agent to provide sulphonic acids dissolved in the blend, removing the spent sulphonating agent, treating the blend containing sulphonic acids with a polyvalent metal base to convert the sulphonic acids to polyvalent metal sulphonate dissolved in the blend, and removing any unreacted polyvalent metal base.

15. A method of preparing a lubricatng oil having reduced tendency toward oxidation, ringsticking, and corrosion which comprises: removing naphthenic acids and other acidic substances from a naphthene base oil whose principal constituents have boiling points above 375 F. at 2 mm. Hg absolute pressure, blending the purified oil with a paraffin base oil of lubricating oil viscosity in amount not greater than 70% of the blend, treating the blend with a sulphonating agent to provide sulphonic acids dissolved in the blend, removing the spent sulphonating agent, treating the blend containing'sulphonic acids with lime in the presence of water to convert the sulphonic acids to calcium sulphonate dissolved in the blend, and removing the water and unreacted lime.

16. A method of preparing a lubricating oil containing polyvalent metal salts of sulphonic acids derived from sulphonating a highly viscous naphthene base oil which comprises: removing naphthenic acids and other acidic substances from a highly viscous naphthene base 011 whose principal constituents have boiling points above 375 F. at 2 mm. Hg absolute pressure, diluting the oil with a low viscosity oil having high resistance to sulphonation, treating the purified and diluted oil with a sulphonating agent to provide sulphonic acids dissolved in the oil, removing the spent sulphonating agent, treating the oil containing sulphonic acids with a polyvalent metal base to convert the sulphonic acids to polyvalcnt metal sulphonate dissolved in the oil, and then re- 4 ARTHUR LAZAR.

JOHN C. CARTER. 

